This is a revised application for an ADAM HA Research Scientist Development Award (K02). The research of the principal investigator (P.I.) has been supported by NIDA grants for the last six years. This behavioral research has provided evidence that taste and diet preferences are mediated in part by opioid mechanisms. Further, diet preferences were found to predict the nature of the feeding response to morphine. Preferences for dietary fat and saccharin were found to be related to subsequent oral self-administration of ethanol, and saccharin preference was observed to be related to the intravenous self-administration of morphine. The involvement of opioids in mediating-diet and taste preferences, and the apparent predictive nature of these preferences in relation to drug self-administration, suggests that high preferences for sweet taste and/or dietary fat may indicate a general propensity to self- administer drugs. This proposal outlines a series of behavioral experiments which will provide an in-depth examination of the interactions between diet/taste preferences (partially opioid-mediated) and intravenous drug self-administration. Specifically, the acquisition and maintenance of self-administration of cocaine and heroin will be examined in rats selected for high or low preferences for fat or saccharin. A subsequent experiment will examine the effects of manipulation of diet composition on drug self-administration. In a third experiment, diet preferences will be manipulated via pre-exposure to high-fat or high-carbohydrate diets; the effects of baseline shifts in diet preference on self-administration will then be assessed. A fourth experiment will examine the effects of drug pre-exposure (sensitization) on the interaction between diet/taste preferences and drug self- administration. The proposed studies represent a logical progression from previous and current research by the P.I., and may provide information which will be valuable in determining vulnerability to drug abuse. Further, the information may provide a basis for improved behavioral, dietary and pharmacological management of eating disorders and drug abuse.